<template>
  <div class=''>
    <input
      id="excel-upload-input"
      ref="excel-upload-input"
      type="file"
      accept=".xlsx,.xls"
      class="c-hide"
      @change="handkeFileChange"
    />
    <label
      style="margin-left:16px;color: #3296fa;border-bottom:1px solid #3296fa;"
      @click="handleUpload"
    >立即上传</label>
  </div>
</template>

<script>
import XLSX from 'xlsx'

export default {
  data () {
    return {
      loading: false,
      excelData: {
        header: null,
        results: null
      }
    }
  },
  methods: {
    generateDate ({ header, results }) {
      this.excelData.header = header
      this.excelData.results = results
      this.$emit('on-selected-file', this.excelData)
    },
    handleDrop (e) {
      e.stopPropagation()
      e.preventDefault()
      const files = e.dataTransfer.files
      if (files.length !== 1) {
        this.$message.error('Only support uploading one file!')
        return
      }
      const itemFile = files[0]
      this.readerData(itemFile)
      e.stopPropagation()
      e.preventDefault()
    },
    handleDragover (e) {
      e.stopPropagation()
      e.preventDefault()
      e.dataTransfer.dropEffect = 'copy'
    },
    handleUpload () {
      document.getElementById('excel-upload-input').click()
    },
    handkeFileChange (e) {
      const files = e.target.files
      const itemFile = files[0]
      if (!itemFile) return
      this.readerData(itemFile)
      this.$refs['excel-upload-input'].value = null
    },
    readerData (itemFile) {
      const reader = new FileReader()
      reader.onload = e => {
        const data = e.target.result
        const fixedData = this.fixdata(data)
        const workbook = XLSX.read(btoa(fixedData), { type: 'base64' })
        const firstSheetName = workbook.SheetNames[0]
        const worksheet = workbook.Sheets[firstSheetName]
        const header = this.get_header_row(worksheet)
        const results = XLSX.utils.sheet_to_json(worksheet)
        this.generateDate({ header, results })
      }
      reader.readAsArrayBuffer(itemFile)
    },
    fixdata (data) {
      let o = ''
      let l = 0
      const w = 10240
      for (;l < data.byteLength / w; ++l) o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w, l * w + w)))
      o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w)))
      return o
    },
    get_header_row (sheet) {
      const headers = []
      const range = XLSX.utils.decode_range(sheet['!ref'])
      let C
      const R = range.s.r
      for (C = range.s.c; C <= range.e.c; ++C) {
        let cell = sheet[XLSX.utils.encode_cell({ c: C, r: R })]
        let hdr = 'UNKNOWN' + C
        if (cell && cell.t) hdr = XLSX.utils.format_cell(cell)
        headers.push(hdr)
      }
      return headers
    }
  }
}
</script>
<style scoped>
#excel-upload-input{
  display: none;
  z-index: -9999;
}
#drop{
  border: 2px dashed #bbb;
  width: 600px;
  height: 160px;
  line-height: 160px;
  margin: 0 auto;
  font-size: 24px;
  border-radius: 5px;
  text-align: center;
  color: #bbb;
  position: relative;
}
</style>
